1. Field of the Invention
The invention relates in general to transport refrigeration systems, and more specifically to transport refrigeration systems for narrow post highway trailers.
2. Description of the Prior Art
There are two types of regrigerated highway trailers, distinguished by the way the front wall of the trailer is supported. The two types are commonly referred to as "narrow post" and "wide post".
Narrow post trailers have the main trailer front wall support structure spaced about three feet (91 cm) apart, and the opening for accommodating a transport refrigeration system mounted on the front wall must fit between the supports of the support structure. This opening is usually twenty eight inches (71 cm) high and thirty seven inches (94 cm) wide. Transport refrigeration systems of the prior art for narrow post trailers conventionally include narrow box type evaporator sections which intrude into the interior trailer space by a dimension which is approximately three feet (91 cm) wide, two and one-half feet (76 cm) high, and three and one-third feet (101 cm) deep.
Wide post trailers have the main trailer front wall support structure spaced about sixty eight inches (173 cm) apart. Front wall openings are usually about forty six inches (117 cm) high and sixty inches (152 cm) wide. Transport refrigeration systems for wide post application are about one-third larger in exterior volume than systems for narrow post application, with the larger volume and large opening to the cargo space permitting innovative system designs which result in a much smaller intrusion of the refrigeration system into the cargo space. For example, systems such as shown in U.S. Pat. Nos. 4,182,134 and 4,551,986, which are assigned to the same assignee as the present application, require only about a four inch (10 cm) intrusion into the cargo space. This intrusion is about the minimum, as it is occupied by ductwork which directs air from the lower part of the trailer into the evaporator section of the refrigeration system.
The minimal intrusion of the wide post transport refrigeration systems into the cargo space, commonly referred to as zero cube units, is a highly desired feature, as it enables substantially all of the cargo space to be used. Thus, it would be desirable to reduce the intrusion of the narrow post transport refrigeration systems into the cargo space, if this can be accomplished without excessively increasing the weight and size of the overall unit package. For example, any rearrangement of the components of the transport refrigeration system must not increase the depth dimension of the unit beyond about 22.3 inches (56.6 cm), i.e., the measurement from the front wall of the trailer towards the tractor.